Xi’an region was the study objects based on ArcGIS engine platform and the information of the Xi’an seismological bureau, the division of the potential seismic source zones and the seismic activity parameters were adopted, according the stochastic finite fault to obtain the ground motion prediction models, taking the discretization algorithm and choosing potential seismic source zones as the basic unit, dividing the potential seismic source zones into grids which are viewed as point sources and the corresponding exceeding probabilities are calculated, that is probabilistic seismic hazard analysis. On the basis of the deaggregation of probabilistic seismic hazard to define the most dangerous levels corresponding the contribution rate of the ground motion intensity measures, according the weighted method to determine the scenario earthquakes. The results show that,the spectrum of acceleration for the three basic periods at 0.2 s, 1.0 s, and 2.4 s, for the same hazard levels, the potential seismic source zones are roughly the same for the site of the larger contribution, but the relative contribution rates have still difference; For the different hazard levels, the potential seismic source zones are difference for the site of the larger contribution, but several potential seismic source zones are close to the site, and more concentrated.